Refrigerating system having reciprocating compressor

ABSTRACT

A refrigerating system includes: an evaporator ( 2 ) for performing a cooling operation as a refrigerant is evaporated; a compressor ( 4 ) for compressing the refrigerant discharged from the evaporator as a mover is reciprocally moved; a condenser ( 6 ) for changing the refrigerant compressed in the reciprocating compressor to a liquid refrigerant; and a capillary tube ( 8 ) for decompressing the refrigerant discharged from the condenser and transferring it to the evaporator. The refrigerant is an HFC refrigerant, hydrogenated carbon fluoride comprising hydrogen, fluorine and carbon and the lubricant is an ester-based lubricant, a sort of synthetic fluid, so that a lubricating performance and a performance of the refrigerating system can be improved.

TECHNICAL FIELD

The present invention relates to a refrigerating system for performing acompressing operation on a refrigerant by a reciprocating compressorand, more particularly, to a refrigerating system having a reciprocatingcompressor that is capable of improving a lubricating performance byenhancing a lubricant used for a reciprocating compressor and thusenhancing a performance of a refrigerating system.

BACKGROUND ART

As chlorofluorocarbon (CFC), a refrigerant used for a refrigerator, anair-conditioner or the like, has been known as a source materialdamaging an ozone layer of the stratosphere, researches on a substituterefrigerant are being actively conducted.

The substitute refrigerant for CFC/HCFC is desired to beenvironment-friendly as well as to have excellent thermodynamical andchemicophysical characteristics. That is, the substitute refrigerantshould have a high energy efficiency, a zero ozone layer disintegrationindex, a low global warming index, no toxic character andincombustibility.

There are a few refrigerants which have no toxicity and nocombustibility and are not CFC among methane-based and ethane-basedhalocarbon compounds: R22, R23, R134a, R123, R124 and R125. Of them,R22, R123 and R124, which are HCFC, are under regulation, and in case ofR23, even though it is a kind of HFC, its thermodynamical property isnot so good as to be utilized as a refrigerant.

HFC pure refrigerants usable as a substitute refrigerant amonghalocarbon are very limited. Thus, mixed refrigerants have been studiedand developed as substitute refrigerants by mixing two or three purematerials at a suitable composition ratio to make up for shortcomings ofthe pure materials and thus obtain a good environment index.

R134a, R152a or cyclopropane (RC270) can substitute R12 which has beenwidely used for the home-use refrigerators and automobileair-conditioners. An HFC mixed refrigerant such as R404A and R507 isbeing taken into account as a substitute refrigerant of R502 mainly usedas a low temperature refrigerant. Meanwhile, HFC mixed refrigerantsincluding R32 are considered as substitute refrigerants of R22 used fora heat pump and various air-conditioning devices. Researches are underway for those substitute refrigerants.

The CFC includes R11 (trichloromonogluoromethane), R12(dichlorodifluoromethane), R113 and the like, of which R12 largely usedas a refrigerant for a refrigerator is one of regulation-subjectmaterials as being a source material causing an ozone layer reductionand generating a global warming effect. Thus, currently, R134a is put toa practical use as a substitute refrigerant of R12.

As a representative example of HCF, R134a exhibits a zero ozonedepletion potential, incombustibility and physical properties similar toR12, and is widely used as such.

However, with all those advantages, R134a is hardly combined withrefrigerant oil currently used for a refrigerating system of R12 due toits peculiar chemical and electrical properties. Therefore, arefrigerant oil suitable for the refrigerant R134a is in need ofdevelopment. Especially, necessity of a refrigerant oil usable for areciprocating compressor for compressing the refrigerant R134a comes tothe front.

FIG. 1 shows a construction of a general refrigerating cycle.

As shown in FIG. 1, a currently used refrigerating cycle includes: anevaporator 2 for performing a cooling operation as a low temperature andlow pressure liquid refrigerant is evaporated; a compressor 4 forcompressing the low temperature and low pressure gaseous refrigerantdischarged from the evaporator 2 to a high temperature and high pressuregaseous refrigerant; a condenser 6 for changing the high temperature andhigh pressure gaseous refrigerant discharged from the compressor 4 to ahigh temperature and high pressure liquid refrigerant; and a capillarytube 8 for decompressing the refrigerant discharged from the condenser 6so as to be easily evaporated and transferring it to the evaporator 2.

The refrigerant used for the refrigerating system is R134a, and arefrigerant oil used for the compressor 4 needs to have such physicaland chemical characteristics that it is well harmonized with therefrigerant R134a.

That is, the refrigerant oil of the refrigerating system should havecharacteristics that it protects a oil film sufficiently even though therefrigerant is dissolved, it is sufficiently stable thermally andchemically so as not to react in spite of being in contact with arefrigerant or an organic material metal, etc. at a high temperature orat a low temperature, and it has a high level of thermal stability so asnot to generate a carbon sludge or not to be oxidized at a hightemperature part of the compressor.

In order to satisfy those characteristics, characters of the lubricant,such as a kinematic viscosity, a pour point, a density, a total acidnumber, a water content or the like, work as critical factors.

Therefore, if the refrigerant oil used for the refrigerating system isnot harmonized with the refrigerant, oil circulation is deteriorated todegrade a heat transfer performance of the refrigerating system and alubrication performance, resulting in that frictional portions of eachmotional part are abraded and thus each part is damaged. Then, theperformance of the refrigerating system is deteriorated.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to provide arefrigerating system having a reciprocating compressor that is capableof improving a lubricating performance and a performance of arefrigerating system by using HFC, hydrogenated carbon fluoride, as arefrigerant for the refrigerating system and using a refrigerant oilwell harmonized with the HFC refrigerant for the reciprocatingcompressor.

To achieve these objects, there is provided a refrigerating system of areciprocating compressor including: an evaporator for performing acooling operation as a refrigerant is evaporated; a reciprocatingcompressor which includes a driving unit having a stator consisting ofan outer stator fixed inside a hermetic container, an inner statordisposed with a certain air gap with an inner circumferential surface ofthe outer stator, and a winding coil wound at one of the outer statorand the inner stator, to which power is applied from an external source,a mover consisting of magnets disposed at regular intervals between theouter stator and the inner stator and linearly and reciprocally movedwhen power is applied to the winding coil and a magnet frame, in whichthe magnets are mounted, for transmitting a linear reciprocal motionalforce to a compression unit, a compression unit for performing acompressing operation on a refrigerant upon receiving the linearreciprocal motional force of the driving unit, and a lubrication unitfor supplying the lubricant, a sort of a mineral oil, to each motionalportion of the driving unit and the compression unit and performing alubricating operation; a condenser for changing the refrigerantcompressed in the reciprocating compressor to a liquid refrigerant; anda capillary tube for decompressing the refrigerant discharged from thecondenser and transmitting it to the evaporator, wherein the refrigerantis an HFC refrigerant, hydrogenated carbon fluoride comprising hydrogen,fluorine and carbon and not including chlorine, and the lubricant is anester-based lubricant, a sort of synthetic fluid, with a high moistureabsorption and a saturated water amount of 1500˜2000 PPM.

In the refrigerating system having a reciprocating compressor of thepresent invention, an L-cord type heater is mounted at a lower portionof the evaporator, of which a heating wire is coated with a siliconmaterial and a coating material made of an aluminum material is coatedat an outer circumferential surface thereof.

In the refrigerating system having a reciprocating compressor of thepresent invention, a controller is additionally provided to vary acapacity of a compressor depending on an ambient temperature andenvironment.

In the refrigerating system having a reciprocating compressor of thepresent invention, the controller determines an output value accordingto a phase difference between a current and a voltage.

In the refrigerating system having a reciprocating compressor of thepresent invention, the magnet is an Nd (neodium) magnet.

In the refrigerating system having a reciprocating compressor of thepresent invention, the refrigerant has a zero ozone depletion potential(ODP) and is incombustible.

In the refrigerating system having a reciprocating compressor of thepresent invention, the refrigerant is HFC134a which has a purity ofabove 99.9%, a molecular formula of CF₃CFH₂, and a molecular weight of102.

In the refrigerating system having a reciprocating compressor of thepresent invention, the lubricant has a density of 0.93˜0.99 g/cm³ at atemperature of 15° C. and a total acid number of below 0.01 mgKOH/g.

In the refrigerating system having a reciprocating compressor of thepresent invention, the lubricant has a flash point of below 240° C. anda kinematic viscosity (cSt) of 10.0˜22.5 mm²/s at a temperature of 40°C.

In the refrigerating system having a reciprocating compressor of thepresent invention, the lubricant contains an additive such as astabilizer or antioxidant, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the construction of a refrigerating cycle of ageneral refrigerating system; and

FIG. 2 is a sectional view of the general reciprocating compressor.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

FIG. 1 illustrates the construction of a refrigerating cycle of ageneral refrigerating system, and FIG. 2 is a sectional view of thegeneral reciprocating compressor.

The refrigerating cycle of the refrigerating system includes: anevaporator 2 for performing a cooling operation as a low temperature andlow pressure liquid refrigerant is evaporated; a compressor 4 forcompressing the low temperature and low pressure gaseous refrigerantdischarged from the evaporator 2 to a high temperature and high pressuregaseous refrigerant; a condenser 6 for changing the high temperature andhigh pressure gaseous refrigerant discharged from the compressor 4 to ahigh temperature and high pressure liquid refrigerant; and a capillarytube 8 for decompressing the refrigerant discharged from the condenser 6so as to be easily evaporated and transferring it to the evaporator.

The refrigerating system includes a controller (not shown) whichdetermines an output value according to a phase difference between acurrent and a voltage in order to vary a capacity of the compressordepending on an ambient temperature and environment.

The evaporator 2 is a fin-tube type evaporator with an L-cord typeheater (not shown) mounted at its lower portion. The L-cord type heaterhas a structure that a heating wire is coated with a silicon materialand a coating material made of aluminum is coated at its outercircumferential surface.

As shown in FIG. 2, the compressor 4 includes: a hermetic container 24to which a suction pipe 20 for sucking a refrigerant and a dischargepipe 22 for discharging a compressed refrigerant; a driving unit 26disposed inside the hermetic container 24 and generating a reciprocalmotional force; a compression unit 28 for performing a compressingoperation on the refrigerant upon receiving a reciprocal motional forcegenerated from the driving unit 26; and a lubrication unit 30 forperforming a lubrication operation on each motional portion of thedriving unit 26 and the compression unit 28.

The driving unit 26 consists of a stator 32 fixed inside the hermeticcontainer 24, and a mover 34 disposed spaced apart from the stator 32and linearly and reciprocally moved by an interaction with the stator 32when power is applied to the stator 32.

The stator 32 includes a cylindrical outer stator 38 fixed by a supportframe 36 fixed inside the hermetic container 24, an inner stator 40disposed with a certain air gap with an inner circumferential surface ofthe outer stator 38, and a winding coil 42 wound inside the outer stator38 to which power is applied from an external source.

The mover 34 includes a magnet 46 disposed with a certain space betweenthe outer stator 38 and the inner stator 40 and linearly andreciprocally moved when power is applied to the winding coil 42, and amagnet holder 48 having magnets 46 mounted at equal intervals at its anouter circumferential surface and being connected to a piston 50 of thecompression unit 28.

The compression unit 28 includes a piston 50 connected to the magnetholder 48 and linearly and reciprocally moved; a cylinder 54 into whichthe piston 50 is slidably inserted to form a certain compression chamber36; a suction valve 58 mounted at a refrigerant passage 56 formed at thepiston 50 and preventing a backflow of the refrigerant after beingintroduced into the compression chamber 52; and a discharge valve 60mounted at the front side of the cylinder 54 and performing an openingand closing operation on a compressed refrigerant.

The lubrication unit 30 includes a lubricant 62 filled with a certainamount at the lower portion of the hermetic container 24; a lubricantpumping unit 68 for pumping the lubricant 62; and a lubricant supplypassage 64 for supplying the lubricant 62 pumped by the lubricantpumping unit 68 to a frictional portion between the piston 50 and thecylinder 54.

The operation of the refrigerating system constructed as described abovewill now be explained.

When the compressor 4 is driven, the low temperature and low pressuregaseous refrigerant is compressed to a high temperature and highpressure gaseous refrigerant, which is then introduced into thecondenser 6 and changed to a liquid refrigerant The liquid refrigerantdischarged from the condenser is decompressed while passing through thecapillary tube 8 and then transferred to the evaporator 2. At this time,air is cooled while passing through the evaporator 2 and supplied intothe refrigerating system, thereby performing a cooling operationtherein.

The operation of the reciprocating compressor will now be described indetail.

When power is applied to the winding coil 42, a flux is formed aroundthe winding coil 42, forming a closed loop along the outer stator 38 andthe inner stator 40. By the interaction of the flux formed between theouter stator 38 and the inner stator 40 and the flux formed by themagnet 46, the magnet 46 is linearly moved in an axial direction. Whenthe direction of a current applied to the winding coil 42 is changed inturn, the magnet 46 is linearly and reciprocally moved as the directionof the flux of the winding coil 42 is changed.

Then, the motion of the magnet 46 is transferred to the piston 50 by themagnet holder 48, and accordingly, the piston 50 is linearly andreciprocally moved inside the cylinder 54, thereby performing acompressing operation on the refrigerant.

That is, when the piston 50 is retreated, the refrigerant introducedinto the suction pipe 20 is supplied to the compression chamber 52through the suction passage 56 formed at the piston 50. Meanwhile, whenthe piston 50 advances, the suction passage 56 is closed by the suctionvalve 58, the refrigerant inside the compression chamber 52 iscompressed, and the compressed refrigerant is externally dischargedthrough the discharge pipe 22

During the compressing operation, the lubricant 62 filled in thehermetic container 24 is pumped according to operation of the lubricantpumping unit 68 and supplied to the frictional portion between thepiston 50 and the cylinder 54 through the lubricant supply passage 64,for a lubricating operation.

As the refrigerant compressed by the reciprocating compressorconstructed and operated as described above, the HFC refrigerant,hydrogenated carbon fluoride comprising hydrogen, fluorine and carbonwithout chlorine, is mainly used as having a high energy efficiency anda zero ODP (ozone depletion potential), is incombustible, and has a lowglobal warming index, no toxicity and incombustibility.

Specifically, R32, R143a and R152a, etc. are used as the HFCrefrigerant, of which HFC134a is preferably used for the currentrefrigerator as it has a purity of above 99.9%, a molecular formulaCF₃CFH₂ and a molecular weight of 102.

As the lubricant of the reciprocating compressor for which the HFC34arefrigerant is used, an ester-based lubricant, a sort of syntheticfluid, is used as it has a good compatibility with the refrigerant andsatisfies physical and chemical characteristics.

The density of the ester-based lubricant is preferably 0.93˜0.99 g/cm³at a temperature of 15° C.

Preferably, a total acid number of the ester-based lubricant is adoptedby below 0.01 mgKOH/g.

The total acid number of the lubricant, representing an amount of anacid component contained in an oil, indicates an amount of potassiumhydroxide required for neutralizing an acid component contained in 1 gof sample oil by the number of mg. Since the lubricant used for therefrigerator should be absolutely neutral, the total acid number worksas a basis for determining a deterioration level of the refrigerant oil.

A flash point of the ester-based lubricant varies depending on a sizeand a type of the reciprocating compressor. Preferably, it is below 240°C., and it can be below 165° C., below 175° C., below 185° C. and below200° C. according to the type of an adopted compressor.

A kinematic viscosity (cSt) of the ester-based lubricant is preferably10.0˜22.5 mm²/s at a temperature of 40° C.

A saturated water amount of the ester-based lubricant is preferably1500˜2000 PPM. The moisture contained in the lubricant should bemaintained by below a suitable level because it causes freezing, sludgegeneration and corrosion.

A breakdown voltage of the ester-based lubricant is preferably above 30KV.

As so far described, the refrigerating system having a reciprocatingcompressor of the present invention has such an advantage that since ituses the ester-based lubricant, a sort of a synthetic fluid, with anexcellent compatibility with the HFC refrigerant, hydrogenated carbonfluoride comprising hydrogen, fluorine and carbon without chlorine, thelubricating performance is improved, a life span of the reciprocatingcompressor is lengthened and a performance of the refrigerating systemcan be enhanced.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the refrigerating systemhaving a reciprocating compressor of the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover modifications and variationsof this invention provided they come within the scope of the appendedclaims and their equivalents.

1. A refrigerating system comprising: an evaporator for performing acooling operation as a refrigerant is evaporated; a reciprocatingcompressor including: a driving unit for generating a linear reciprocalmotional force, a compression unit for compressing the refrigerant uponreceiving the linear reciprocal motional force of the driving unit, anda lubrication unit for supplying a lubricant to each motional portion ofthe driving unit and the compression unit and performing a lubricatingoperation; a condenser for changing the refrigerant compressed in thereciprocating compressor to a liquid refrigerant; and a capillary tubefor decompressing the refrigerant discharged from the condenser andtransmitting it to the evaporator, wherein the refrigerant is ahydrofluorocarbon (HFC) refrigerant, and the lubricant is an ester-basedlubricant with a high moisture absorption and a saturated water amountof 1500˜2000 PPM, and wherein the refrigerant is HFC134a which has apurity of above 99.9%, a molecular formula of CF₃CFH₂, and a molecularweight of
 102. 2. The refrigerating system of claim 1, wherein themagnet is an Nd (neodium) magnet.
 3. The refrigerating system of claim1, wherein the refrigerant has a zero ozone depletion potential (ODP)and is incombustible.
 4. The refrigerating system of claim 1, whereinthe lubricant contains an additive including a stabilizer orantioxidant.
 5. The refrigerating system of claim 1, wherein the drivingunit includes a stator having an outer stator fixed inside a hermeticcontainer, an inner stator disposed with a certain air gap with an innercircumferential surface of the outer stator, and a winding coil wound atone of the outer stator and the inner stator, to which power is appliedfrom an external source, a mover having magnets disposed at regularintervals between the outer stator and the inner stator and linearly andreciprocally moved when power is applied to the winding coil and amagnet frame, in which the magnets are mounted.
 6. A refrigeratingsystem comprising: an evaporator for performing a cooling operation as arefrigerant is evaporated; a reciprocating compressor including: adriving unit for generating a linear reciprocal motional force, acompression unit for compressing the refrigerant upon receiving thelinear reciprocal motional force of the driving unit, and a lubricationunit for supplying a lubricant to each motional portion of the drivingunit and the compression unit and performing a lubricating operation; acondenser for changing the refrigerant compressed in the reciprocatingcompressor to a liquid refrigerant; and a capillary tube fordecompressing the refrigerant discharged from the condenser andtransmitting it to the evaporator, wherein the refrigerant is ahydrofluorocarbon (HFC) refrigerant, and the lubricant is an ester-basedlubricant with a high moisture absorption and a saturated water amountof 1500˜2000 PPM, and wherein the lubricant has a density of 0.93˜0.99g/cm³ at a temperature of 15° C. and a total acid number of below 0.01mgKOH/g.
 7. The refrigerating system of claim 6, wherein the drivingunit includes a stator having an outer stator fixed inside a hermeticcontainer, an inner stator disposed with a certain air gap with an innercircumferential surface of the outer stator, and a winding coil wound atone of the outer stator and the inner stator, to which power is appliedfrom an external source, a mover having magnets disposed at regularintervals between the outer stator and the inner stator and linearly andreciprocally moved when power is applied to the winding coil and amagnet frame, in which the magnets are mounted.
 8. A refrigeratingsystem comprising: an evaporator for performing a cooling operation as arefrigerant is evaporated; a reciprocating compressor including: adriving unit for generating a linear reciprocal motional force, acompression unit for compressing the refrigerant upon receiving thelinear reciprocal motional force of the driving unit, and a lubricationunit for supplying a lubricant to each motional portion of the drivingunit and the compression unit and performing a lubricating operation; acondenser for changing the refrigerant compressed in the reciprocatingcompressor to a liquid refrigerant; and a capillary tube fordecompressing the refrigerant discharged from the condenser andtransmitting it to the evaporator, wherein the refrigerant is ahydrofluorocarbon (HFC) refrigerant, and the lubricant is an ester-basedlubricant with a high moisture absorption and a saturated water amountof 1500˜2000 PPM, and wherein the lubricant has a flash point of below240° C. and a kinematic viscosity (cSt) of 10.0˜22.5 mm²/s at atemperature of 40° C.
 9. The refrigerating system of claim 8, whereinthe driving unit includes a stator having an outer stator fixed inside ahermetic container, an inner stator disposed with a certain air gap withan inner circumferential surface of the outer stator, and a winding coilwound at one of the outer stator and the inner stator, to which power isapplied from an external source, a mover having magnets disposed atregular intervals between the outer stator and the inner stator andlinearly and reciprocally moved when power is applied to the windingcoil and a magnet frame, in which the magnets are mounted.